Leading Nutritionist Shares Tips for a Healthy, Immune-Boosting Diet

A well-balanced diet can lower your risk of developing breast cancer and even improve your outcome rates after a diagnosis, among numerous other benefits. But many Americans struggle to eat the recommended amounts of vegetables, fruits, and whole grains—and that’s during normal times.

Now add in a pandemic where millions are trying to avoid trips to the grocery store, are out of work and unable to afford groceries, and are navigating shortages in their communities. So, how can breast cancer patients, survivors, and everyone else maintain a healthy diet now?

Who better to discuss this than BCRF researcher Dr. Walter Willett, professor of epidemiology and nutrition at Harvard’s T.H. Chan School of Public Health and the most-cited nutritionist in the world. Here, and in the video above, he talks to BCRF about what to eat and how to stay healthy at home. Of course, be sure to talk to your doctor before making any changes to your diet or adding a supplement.

What’s your research focus?

For our work related to breast cancer, we conduct large, long-term epidemiologic studies. We began looking at risk factors for breast cancer back in the 1970s. And since 1980, diet has been a very central part of our research, first learning what aspects of diet and lifestyle might be related to lower risk or higher risk of breast cancer. More recently—now that we’ve been able to track more than 200,000 women who have developed breast cancer for decades—we’re looking at factors that can influence survival after breast cancer. Many members of our team do this work. It involves conducting laboratory measurements of hormones, nutrients, and other dietary data, and getting biological samples from tumors. I think it’s fair to say, we have the most detailed, long-term look at factors that influence risk of breast cancer and overall wellbeing.

During the COVID-19 pandemic, we’re trying to minimize our trips to the grocery store and still eat well. Can you make any recommendations for nutrient dense produce or other staples that last?

This is a very important question because now is especially the time to be eating a healthy diet. It’s always a good thing to do, but in the event that we are exposed to the COVID-19 virus, we want to be in the best possible physical shape to be the most resilient. It’s not a by accident that the factors that are related most strongly to adverse outcomes from COVID-19 outside of age are obesity, diabetes, heart disease, and hypertension. These are all strongly related to nutrition. But it’s also more challenging to make sure our diets are well-balanced right now both in terms of the availability of food and the fact that a lot of people have lost their jobs. Cost is becoming a real issue for many people.

Stock up on whole grains: brown rice, quinoa, whole-grain pasta. Beans and lentils often get lost in the American diet, but they’re a staple of diets all around the world and good protein sources with lots of minerals and vitamins. I’d also include nuts and peanut butter as staples. Sometimes people don’t think of those, but they have a long shelf life. It’s good to keep nuts in the refrigerator or freezer to preserve their freshness. Healthy oils are a crucial part of a balanced diet too: olive oil, canola oils, pretty much all the liquid vegetable oils are good.

As far as vegetables and fruits, those are a little more difficult since they tend to be more perishable. But still, many can last a long time. Before we had modern refrigeration, we stocked up carrots, sweet potatoes, winter squash, and cabbage to get us through winter. Those are tremendously good sources of micronutrients and phytochemicals, and again, they can be used in many different ways. Greens like spinach, kale, and collards are often a weak spot in many diets. In fact, in our surveys we found about 50 percent of Americans eat almost no greens. Whether we’re in a pandemic or not, it’s important to think about those foods. I might also add orange juice as a staple. For decades and decades, it’s been good source of vitamin C.

Fresh vegetables may be more difficult to obtain and have a shorter shelf life, but frozen is good as well. I don’t really think we need to be getting fresh tomatoes all year long. Canned tomatoes can have more micronutrients and be made into soups and many other dishes.

What is the relationship between nutrition and immunity? How does what we eat affect how well we’re able to fight off infection and viruses?

We’ve learned a lot about nutrition and immunity over the years, and the bigger picture that emerges is that if we have gaps in one of many different essential nutrients—vitamin C, zinc, vitamin A—we will be more susceptible to infections or end up with more serious forms if we do get infected. So, the most important thing is to make sure we don’t have any gaps in our nutritional defenses. But it doesn’t mean that because those are essential and critical nutrients that just adding more is better.

I make an analogy with a car. You’ve got to have all these different parts, and they all need to be working for it to run. If any one of them falls out or isn’t working, the whole thing may not work. But just adding another of the same part doesn’t necessarily make it better. Adding a fifth wheel won’t fix the problem and might make it worse.

People, of course, would like to have a superfood or super-nutrient to eat a lot of. We don’t really have such a thing as a superfood that will make us super-immune. That’s why we go back to the completeness of a diet again and again.

What nutrients are commonly neglected?

Vitamin D. Our natural source is not primarily from our diets. It’s sun exposure. When the sun hits our skin, we generate vitamin D. Fish has a little bit of vitamin D, but you’re not really going to get much vitamin D unless you eat a lot of fish. This is a precarious time for vitamin D for many people. We’re told to be inside more of the time, missing out on sunlight.

This is especially important for people with darker skin. Because melanin protects the skin and blocks ultraviolet rays, people with darker skin have much lower levels of vitamin D than those with lighter skin. Vitamin D deficiency is 17 times more likely to be present in black Americans compared to white Americans.

Unless someone is really confident that they have adequate vitamin D levels—either having them checked by a doctor or because they’re out in the sun a lot—I think it makes sense for most people to take a vitamin D supplement. There is still a lot of disagreement and discussion about what the optimal dose is. I think about 2000 international units (IU) a day is a good dose for most people, up to an upper limit of 4000 IU. For people with darker skin, a dosage closer to 4000 IU may make sense.

There’s been a meta-analysis of many randomized trials, and vitamin D has been shown to reduce respiratory infections. Some of those include different coronaviruses, as well. That’s why a number of people have suggested, particularly in the COVID-19 era, that we take a vitamin D supplement to make sure we’re not low. But again, this does not replace a healthy diet.

On the subject of supplements, are there any others you recommend with a balanced diet, especially now?

Even before this pandemic, I’ve thought it makes sense for most people to take a standard multivitamin/mineral. It’s a bit like an insurance policy so we don’t have any gaps in our diet. I’m not talking about expensive mega-doses here. Many people, even if they think they’re eating healthy diet, can have some gaps other than vitamin D.

People over the age of 50 are often not absorbing vitamin B-12 very well because their stomachs aren’t making enough acid to promote absorption. Premenopausal women are often low in iron because of menstrual losses. So just the standard multivitamin/mineral will take care of those gaps pretty effectively.

If you had to give one piece of nutritional advice at this time for breast cancer patients and everyone, what would it be?

I would go back to my first comment. Eat a healthy, balanced diet as best we possibly can.